1<refentry id="vidioc-enum-fmt"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_ENUM_FMT</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_ENUM_FMT</refname> 9 <refpurpose>Enumerate image formats</refpurpose> 10 </refnamediv> 11 12 <refsynopsisdiv> 13 <funcsynopsis> 14 <funcprototype> 15 <funcdef>int <function>ioctl</function></funcdef> 16 <paramdef>int <parameter>fd</parameter></paramdef> 17 <paramdef>int <parameter>request</parameter></paramdef> 18 <paramdef>struct v4l2_fmtdesc 19*<parameter>argp</parameter></paramdef> 20 </funcprototype> 21 </funcsynopsis> 22 </refsynopsisdiv> 23 24 <refsect1> 25 <title>Arguments</title> 26 27 <variablelist> 28 <varlistentry> 29 <term><parameter>fd</parameter></term> 30 <listitem> 31 <para>&fd;</para> 32 </listitem> 33 </varlistentry> 34 <varlistentry> 35 <term><parameter>request</parameter></term> 36 <listitem> 37 <para>VIDIOC_ENUM_FMT</para> 38 </listitem> 39 </varlistentry> 40 <varlistentry> 41 <term><parameter>argp</parameter></term> 42 <listitem> 43 <para></para> 44 </listitem> 45 </varlistentry> 46 </variablelist> 47 </refsect1> 48 49 <refsect1> 50 <title>Description</title> 51 52 <para>To enumerate image formats applications initialize the 53<structfield>type</structfield> and <structfield>index</structfield> 54field of &v4l2-fmtdesc; and call the 55<constant>VIDIOC_ENUM_FMT</constant> ioctl with a pointer to this 56structure. Drivers fill the rest of the structure or return an 57&EINVAL;. All formats are enumerable by beginning at index zero and 58incrementing by one until <errorcode>EINVAL</errorcode> is 59returned.</para> 60 61 <table pgwide="1" frame="none" id="v4l2-fmtdesc"> 62 <title>struct <structname>v4l2_fmtdesc</structname></title> 63 <tgroup cols="3"> 64 &cs-str; 65 <tbody valign="top"> 66 <row> 67 <entry>__u32</entry> 68 <entry><structfield>index</structfield></entry> 69 <entry>Number of the format in the enumeration, set by 70the application. This is in no way related to the <structfield> 71pixelformat</structfield> field.</entry> 72 </row> 73 <row> 74 <entry>&v4l2-buf-type;</entry> 75 <entry><structfield>type</structfield></entry> 76 <entry>Type of the data stream, set by the application. 77Only these types are valid here: 78<constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>, 79<constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant>, 80<constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>, and custom (driver 81defined) types with code <constant>V4L2_BUF_TYPE_PRIVATE</constant> 82and higher.</entry> 83 </row> 84 <row> 85 <entry>__u32</entry> 86 <entry><structfield>flags</structfield></entry> 87 <entry>See <xref linkend="fmtdesc-flags" /></entry> 88 </row> 89 <row> 90 <entry>__u8</entry> 91 <entry><structfield>description</structfield>[32]</entry> 92 <entry>Description of the format, a NUL-terminated ASCII 93string. This information is intended for the user, for example: "YUV 944:2:2".</entry> 95 </row> 96 <row> 97 <entry>__u32</entry> 98 <entry><structfield>pixelformat</structfield></entry> 99 <entry>The image format identifier. This is a 100four character code as computed by the v4l2_fourcc() 101macro:</entry> 102 </row> 103 <row> 104 <entry spanname="hspan"><para><programlisting id="v4l2-fourcc"> 105#define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24)) 106</programlisting></para><para>Several image formats are already 107defined by this specification in <xref linkend="pixfmt" />. Note these 108codes are not the same as those used in the Windows world.</para></entry> 109 </row> 110 <row> 111 <entry>__u32</entry> 112 <entry><structfield>reserved</structfield>[4]</entry> 113 <entry>Reserved for future extensions. Drivers must set 114the array to zero.</entry> 115 </row> 116 </tbody> 117 </tgroup> 118 </table> 119 120 <table pgwide="1" frame="none" id="fmtdesc-flags"> 121 <title>Image Format Description Flags</title> 122 <tgroup cols="3"> 123 &cs-def; 124 <tbody valign="top"> 125 <row> 126 <entry><constant>V4L2_FMT_FLAG_COMPRESSED</constant></entry> 127 <entry>0x0001</entry> 128 <entry>This is a compressed format.</entry> 129 </row> 130 <row> 131 <entry><constant>V4L2_FMT_FLAG_EMULATED</constant></entry> 132 <entry>0x0002</entry> 133 <entry>This format is not native to the device but emulated 134through software (usually libv4l2), where possible try to use a native format 135instead for better performance.</entry> 136 </row> 137 </tbody> 138 </tgroup> 139 </table> 140 </refsect1> 141 142 <refsect1> 143 &return-value; 144 145 <variablelist> 146 <varlistentry> 147 <term><errorcode>EINVAL</errorcode></term> 148 <listitem> 149 <para>The &v4l2-fmtdesc; <structfield>type</structfield> 150is not supported or the <structfield>index</structfield> is out of 151bounds.</para> 152 </listitem> 153 </varlistentry> 154 </variablelist> 155 </refsect1> 156</refentry> 157 158<!-- 159Local Variables: 160mode: sgml 161sgml-parent-document: "v4l2.sgml" 162indent-tabs-mode: nil 163End: 164--> 165